You can create a sloped surface by changing properties of its boundary lines.
You can use this method for the following elements:
- roofs
- soffits
- floors
- structural floors
- ceilings
- If you know the starting height of the slope
and the pitch 
, specify properties for a single sketch line. Revit calculates the position of the opposite edge of the sloped surface. - If you know the height of the lower edge and upper edge
of the sloped surface, but not its pitch , specify properties for parallel sketch lines. Revit calculates the pitch.